Generally, a washing machine is an electric appliance which is able to remove various contaminants attached to clothes, beddings and wearable items (hereinafter, laundry) by using emulsion action of detergent, friction of water currents generated by rotation of a pulsator or drum and shock applied to laundry. A full-automatic washing machine which is introduced recently performs a series of cycles including washing, rinsing and dry-spinning courses automatically, without a manual operation.
In recent, demands for drum type washing machines have been increasing gradually, because drum type washing machines can reduce an overall height and generate no problems of wrinkles and tangle generated in laundry, compared with pulsator type washing machines.
To put a structure of the drum type washing machine mentioned above simply, the drum type washing machine includes a cabinet which defines an exterior appearance thereof, a tub located in the cabinet, with being supported by a damper and a spring, to receive wash water therein, and a cylindrically-oriented drum located in the tub to receive laundry therein. A driving force is transferred to the drum is by a driving part to wash the laundry loaded into the drum.
Such the drum type washing machine having the structure mentioned above generates vibration because of a rotational force of the drum generated when it is rotated and eccentricity of the laundry as an inevitable consequence. The vibration generated by the rotation of the drum is transferred outside via the tub and the cabinet.
Because of that, it is necessary to provide the spring and the damper provided between the tub and the cabinet to suspend and dampen the vibration of the tub and to prevent the vibration transferred to the tub from the drum from transferred to the cabinet.
In the meanwhile, the drum type washing machine mentioned above is installed in an existing installation environment (for example, a sink environment or a built-in environment), not installed separately. As a result, the dimension of the drum type washing machine has to be limited by an installation environment.
It is limited to change an internal structure of such the drum type washing machine for the structure of the spring and damper provided between the tub and the cabinet to suspend and dampen the vibration, as mentioned above. Also, it is limited to change the dimension of the washing machine, because the installation environment of the drum type washing machine is limited.
A lot of searches and developments have been in progress about increase of a washing capacity of the washing machine to improve the amount of washing objects and users convenience recently. However, it is quite difficult in the structure of the conventional drum type washing machine to improve the dimension of the tub to improve the washing capacity, because of the limited conditions mentioned above.
In the meanwhile, the washing machine may be classified into a washing-only device with only a washing function and a washing machine with a drying function.
The washing machine having the drying function may be classified based on the structure or type into a drum type drying machine capable of drying laundry through rotating and tumbling of the laundry performed by a rotatable drum and a cabinet type drying machine capable of drying the laundry that is hung therein.
The drum type washing machine having the drying function may include a cabinet which defines an exterior appearance thereof, a tub mounted in the cabinet and a drum rotatably mounted in the tub.
In addition, a dry duck where dry air is circulated, a heater and a ventilation fan which are installed in the dry duck and a condensation duct where damp air used in drying is circulated and condensed may be provided outside the tub. Auxiliary air-cooled or water-cooled type condensation means used for condensation may be provided in the condensation duct.
Hot air is supplied to the laundry in the conventional washing machine by control of a heater, in other words, by On/Off of a heater. However, the heater control may control On/Off of the heater in reference to the temperature of the heater or the temperature near the heater. Because of that, the conventional washing machine has a problem of failure in preventing the overheating which might be generated at a specific spot on an entire passage where air is circulated.
More specifically, the hot water which is heated after dehumidified may be supplied between the heater and the drum, and heat exchange may be performed in the drum or the tub. After that, the hot air heat-exchanged after dehumidified may be drawn into the heater again. As a result, the possibility of the overheating generated on the heated-air passage between the heater and the drum can be growing disadvantageously. This is because it can be said that there is no object of efficient heat transfer such as a water element on such the passage. Especially, as the heated-air is constantly supplied in an initial stage of the heated-air supply, the possibility of the overheating on the heated-air passage between the heater and the drum seems to be growing more.
Such the overheating may generate heat distortion or damage of elements. Because of that, there may be a concern of deteriorated stability and reliability of the washing machine.
In addition, the washing machine having the drying function according to the prior art determines a timing of determining whether drying of laundry is complete by using a temperature sensor provided in the dry duct. That is, the temperature of the heated-air collected after drying the laundry is measured repeatedly, to determine an end timing of the drying.
However, it is impossible to precisely sense the end timing of the drying by using the temperature of the heated-air. Because of that, the drying is performed for a less time period that fails to reach the end timing of the drying and the laundry happens to be not dried sufficiently. Or, the drying is performed for a more time period that passes the end timing of the drying and the laundry happens to damage accordingly.
To determine the end timing of the drying, the drying time is set sweepingly by sensing the amount or humidity of the laundry simply. Once the set drying time passes, the drying is set to stop. However, the drying end timing of the drying of the laundry performed according to the operation of such the drying module may be set different based on a type of the laundry and a relative humidity. As a result, an actual drying end time may be different from the preset drying time.
Therefore, the conventional washing machine having the drying function may have a problem of incomplete laundry drying because of external condition change. In this case, the user has to operate additional drying of the laundry inconveniently. Also, it has a problem of too much drying performed for the laundry because of external condition change. In this case, damage to the laundry might be generated by too much heated-air. As a result, it is required to sense the precise drying end timing.